1. Field of the Invention
The present invention relates to a thin-film magnetic head material including a detection element for detecting an amount of processing and a method of manufacturing such a head material and to a method of manufacturing thin-film magnetic heads through the use of a detection element.
2. Description of the Related Art
A flying-type thin-film magnetic head used for a magnetic disk device and so on is generally made up of a thin-film magnetic head slider (that may be simply called a slider) having a thin-film magnetic head element provided at the trailing edge of the slider. The slider generally comprises a rail whose surface functions as a medium facing surface (an air bearing surface) and a tapered section or a step near the end on the air inflow side. The rail flies slightly above the surface of a recording medium such as a magnetic disk by means of air flow from the tapered section or step.
A thin-film magnetic head element generally used is a composite-type element made up of layers of an induction magnetic transducer for writing and a magnetoresistive (MR) element for reading.
In general, such thin-film magnetic head sliders are formed through cutting a wafer in one direction in which sections to be sliders (called slider sections in the following description) each including a thin-film magnetic head element are arranged in a plurality of rows. A block called a bar in which the slider sections are arranged in a row is thereby formed. Rails are then formed in the bar and the bar is cut into the sliders.
The manufacturing process of the sliders includes a step of processing the medium facing surface of the bar, that is, grinding or lapping the medium facing surface and a step of cutting the wafer into the bars. The order of the step of processing the medium facing surface and the step of cutting the wafer into the bars depends on methods of processing the medium facing surface and cutting the wafer, as described later.
In the step of processing the medium facing surface, it is required that the MR height and the throat height of the thin-film magnetic head element formed in the bar each fall within a tolerance range and that processing accuracy of the surface processed falls within a tolerance range. The MR height is the length (height) between the end of the MR element close to the medium facing surface and the opposite end. The throat height is the length (height) of the magnetic pole of an induction magnetic transducer.
In the step of processing the medium facing surface, in order to precisely control the MR height and throat height of each thin-film magnetic head element included in a bar, one of the methods taken is to form a detection element (that may be called a lapping guide) in a wafer in advance for detecting an amount of processing. A signal outputted from the detection element is monitored during the step of processing the medium facing surface and the processing is controlled with high accuracy, in response to the output signal. The detection element may be a resistance element whose resistance value changes in response to its dimensions.
To monitor a signal outputted from the detection element in the step of processing the medium facing surface, it is required to form an electrode for monitoring and a lead (conductor) for monitoring in the wafer in advance, in addition to the detection element. The electrode is used for electrically connecting the detection element to a controller of an external processing apparatus. The lead is used for electrically connecting the electrode to the detection element.
FIG. 13 shows an example of arrangement of detection elements, and electrodes and leads for monitoring in a wafer used for manufacturing thin-film magnetic heads of related art. In this example, thin-film magnetic head elements 101 are aligned in a plurality of rows in the wafer 100. The head elements 101 each include: an element section 102 including an induction-type magnetic transducer and an MR element; and a plurality of electrodes 103 for electrically connecting the element section 102 to an external device. In the wafer 100 in the example shown in FIG. 13, between every adjacent head elements 101 in each row, there are a detection element 111 for detecting an amount of processing, two electrodes 112a and 112b for monitoring, and two leads 113a and 113b for monitoring that electrically connect the electrodes 112a and 112b to each other.
FIG. 14 shows another example of arrangement of detection elements, and electrodes and leads for monitoring in a wafer used for manufacturing thin-film magnetic heads of related art. This example may be the one disclosed in Japanese Patent Application Laid-open Hei 8-287424 (1996). In this example, as in the example shown in FIG. 13, the detection element 111, the two electrodes 112a and 112b for monitoring, and the two leads 113a and 113b for monitoring are placed between every adjacent head elements 101 in each row in the wafer 100. One of the electrodes 112a is used for grounding and functions as one of the electrodes 103 of the head element 101 as well.
In the example shown in FIG. 13, the detection element 111, the electrodes 112a and 112b, and the leads 113a and 113b are placed between every adjacent head elements 101 in each row. As a result, the pitch of the head elements 101 in each row is increase by the space occupied by the detection element, the electrodes and the leads, compared to a case where none of these is placed between every adjacent head elements. Consequently, the number of thin-film magnetic head elements obtained from a given length of bar is reduced.
In the example shown in FIG. 14, compared to the one shown in FIG. 13, the pitch of the head elements 101 in each row is reduced and the number of thin-film magnetic head elements obtained from a given length of bar is thereby increased. However, in this example, too, the electrode 112b is additionally provided between every adjacent head elements 101 in each row. Therefore, the pitch of the head elements 101 in each row is still greater, and the number of head elements obtained from a given length of bar is reduced, compared to a case where the electrode 112b is not placed. In particular, since the electrode such as the electrode 112b is required to be connected to a bonding wire, it is necessary to maintain the electrode at a certain size. The pitch is therefore further required to be increased. For example, if the diameter of the bonding wire is about 30 .mu.m, the length of one side of the electrode 112b is required to be about 100 .mu.m.
In the example shown in FIG. 14, the electrode 112a functions as one of the electrodes 103 of the thin-film magnetic head element 101, too. As a result, if the bar is cut at the detection element 111 for dividing the bar into head elements (sliders), part of the lead for monitoring remains exposed outside. The part of the lead may catch noises and cause static damage.